Field of the Invention
The present invention relates to a process for controlling an imaging region of an imaging device.
Description of the Related Art
In a conventionally known network camera system, such as a security or surveillance system, a camera transmits an image captured by the camera to a terminal device through a network. To control the specific area, object or target being imaged, an image capturing direction (angle) or a zoom value (magnification or focal length) of the camera is changed in accordance with an instruction from the terminal device.
Japanese Patent Application Laid-Open No. 2009-130878 has disclosed a technique for controlling, if a user has specified any rectangular region on a captured image on a display screen of a terminal device, the zoom value of a camera so that the captured image in the specified region is magnified.
First, upon the specification of a region on the captured image by the user, the image capturing direction of the camera is changed so that a subject in the specified region comes to the center of the captured region of the camera.
Next, the zoom value of the camera is increased to magnify the display of the image of the subject in the center of the captured image after the image capturing direction is changed. For example, the zoom value is determined so that the captured image in the user specified region comes to be displayed on the entire screen of the area for displaying the captured image. In the technique according to Japanese Patent Application Laid-Open No. 2009-130878, the zoom value is determined based on the dimension ratio between the display region of the captured image and the region selected by the user.
Further, Japanese Patent Application Laid-Open No. 2009-130878 describes the restriction of the zoom value of the camera in accordance with a misalignment amount between the optical axis of the zoom lens and the center of the imaging element caused in the assembly of the imaging element and the zoom lens to the camera.
In the technique according to Japanese Patent Application Laid-Open No. 2009-130878, however, if the zooming process is performed while the camera captures an image in a particular direction, the subject within the user selected region may not be displayed partly or entirely on the display screen after the zooming process.
Description is made of an example in which the center of a user specified region on the captured image does not coincide with the center of the image capturing direction of the camera because the movable range of the mechanism that changes the image capturing direction of the camera is physically restricted. In such a case, the center of the captured image displayed on the terminal device before the zooming does not coincide with the center of the user selected region on the captured image if zooming.
If the zooming process of the camera is performed, the subject in the center of the captured image is magnified and another subject apart from the center of the captured image is cut out of the display screen (not shown). If the center of the user selected region is apart from (not aligned with) the center of the captured image before the zooming, when the zooming process of the camera is performed, the subject included in the selected region may not be displayed on the display screen at all.